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The “clockwork orange” Earth

23Mar 2012

So a paper I was on got some press this week… and for a change it was a paper that I wanted to get some attention. It contained, ya know… data and stuff. What did it say? Well, it was all about the atmosphere of the Earth at a time when there is had none of the oxygen gas we breathe. If that wasn’t strange enough, there have been proposals (including by yours truly) that it had an “organic haze.” And no… that isn’t just the Whole Foods version of 4loco. Instead, it’s this:

That is, more or less, what people have proposed the early Earth may have looked like from time to time. What we did in this study was look at a lot of data from the rock record. Specifically, lead author Aubrey Zerkle found one data set (in the form of carbon isotope trends) that suggests there were periodic increases to the biological production of methane. Another data set (from analyses of sulfur isotopes) suggests that at the very same time, something was changing the flux of ultraviolet light to the lower atmosphere. The connection between these two phenomena is an organic haze that blocks out UV radiation.

To help interpret Dr. Zerkle’s data, we (really, Mark Claire) ran some atmospheric models. These models showed two things: 1.) an increase in methane flux would have caused a thicker haze; and 2.) the atmosphere would have been “bi-stable” and may have bounced between thick-haze and haze-free (or thin-haze) states. The modeling provides an explanation for the data, because it gives a reason why periodic methane production increases could lead to increases to a haze.

So why should you care? Well, for one… this is just cool/wacky stuff. Imagine our home planet, without any of the air you and I breathe, and in its place a thick, smog-filled atmosphere that blocked out most of the incoming sunlight. For another, this is another example of just how deep the connections are between the planet, its atmosphere, and its climate. Remember, we’re claiming the changes to the atmosphere were brought about by changes to biological methane production. These atmospheric changes would have included a haze that blocked out most of the incoming sunlight. That, in turn, would have had drastic effects on the surface temperature of the planet… and in turn, on the biota living there. These connections are at the heart of our current debates on climate change, but they also extend back throughout the history of life on Earth.